Encrypted ZFS Volume has Disappeared

[briansz]

I have a desktop PC with Mint 20.1, a 512GB boot SSD, and two 2TB HDDs that were set up as a mirrored ZFS volume.

Some time in December, something happened (presumably an update that I initiated) that resulted in me no longer being able to access the ZFS volume. My boot SSD is encrypted, as was the ZFS volume. This is a PC that stays up and running, but it is used sparingly, so I did not notice the problem until recently.

Typically, on reboot, I give the passphrase to unlock the boot SSD, login to my desktop, and when I click the 2TB ZFS volume icon for the first time I am prompted for the passphrase to unlock that volume. Now, I get no prompt for the 2TB passphrase and the volume mounts as completely blank with 0 items and 2.0TB free. Gparted shows that the individual volumes still exist, but that they are not mounted, even when the file manager thinks they are.

https://drive.google.com/file/d/1PD5iSQ ... sp=sharing
https://drive.google.com/file/d/1F7F6YM ... sp=sharing
https://drive.google.com/file/d/19FuL8H ... sp=sharing
https://drive.google.com/file/d/1Tv3BiZ ... sp=sharing

Running df in the terminal shows /dev/md0p1 is being recognized.

Various zfs command line tools I've tried are unable to see the pool. I am thinking this has something to do with the pool not having been unlocked with the correct passphrase.

This has always just worked in the past, so I don't have any idea how I might go about manually forcing the encrypted volume to mount or troubleshooting further. When I initally set up the ZFS pool, it was on an earlier version of Mint. I was able to then get it working on 20.1 with no problems once I'd changed motherboards and upgraded the OS.

Thanks in advance for any assistance.

[mikeflan]

I may not be much help, but I'll bump this for you.
Please start Disks, mount the drive, highlight the partition that is having the problem, and post the disks display. Here is mine:

[t42]

Unlike Ububtu LM Mint has no native ZFS support and fs losses were reported after Mint upgrade. It was hard to say anything after "Various zfs command line tools I've tried". It is about root troubleshooting but the approach can be useful" Using Ubuntu 20.04 live CD